One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,5)(4,7)(6,8)(11,15)(14,16)(17,18,21,23)(19,20,24,22)(26,30)(27,33)(28,36)(39,40)(1,3)(2,4)(5,8)(6,7)(17,19)(18,22)(20,23)(21,24)(25,26,29,30)(27,31,33,34)(28,37,36,32)(35,40,38,39)(1,4,6,5)(2,7,8,3)(9,10,13,12)(11,14,15,16)(17,19,21,24)(18,20,23,22)(25,26)(27,34)(28,37)(29,30)(31,33)(32,36)(35,39)(38,40)(1,5,6,4)(2,3,8,7)(9,11)(10,14)(12,16)(13,15)(17,20,21,22)(18,19,23,24)(25,27)(26,31)(28,38)(29,33)(30,34)(32,40)(35,36)(37,39)(1,3)(2,5)(4,8)(6,7)(9,12,13,10)(11,16,15,14)(17,19)(18,20)(21,24)(22,23)(25,28)(26,32)(27,35)(29,36)(30,37)(31,39)(33,38)(34,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.